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The Adriatic Sea, located in the northernmost part of the Med Sea, represents an important study site for for rapid climatology impacts, due to its topographical, hydrological features and complex circulation patterns. Its southern part is a highly oligotrophic environment where picophytoplankton are the main primary producers and the carbon/energy is transported mainly via the microbial food web. The aim of this study was to investigate the spatial distribution of the picoplankton community along the transect from Dubrovnik to South Adriatic Pit. The samples were taken at eight stations in early March 2016 as a part of BIOTA (Bio-tracing Adriatic Water Masses) project. Bacteria, picocyanobacteria and heterotrophic nanoflagellates were determined and enumerated by flow cytometry. Synechococcus dominated the surface photosynthetic community with maximal abundances up to 2.7 x 104 cells/mL with the high numbers recorded at stations both closer and further from the nearshore area (stations P120, P800). Prochlorococcus abundances were below 2.0 x 104 cells/mL, except at station P600 where 2.5 x 104 cells/mL were recorded. Picoeukaryotes were more abundant at stations farther from the coast, with abundances up to 9.2 x 103 cells/mL. Heterotrophic bacteria were separated into HNA and LNA subpopulations with total numbers up to 1.8 x 105 and 8.8 x 105 cells/mL, respectively. HNA populations dominated at offshore stations reaching their maximum at depths below the euphotic zone. Heterotrophic flagellates were present in low numbers, between 1.3 x 102 and 1.2 x 103, and generally were more abundant at the surface of nearshore stations.

The Gulf of Naples (Central Tyrrhenian Sea, Western Mediterranean Sea) extends between 40°50'-40°32'N and 13°52'-14°28'E, with an area of 870 km2 and an average depth of 170 m. About 4 million people live along the coasts, which have been inhabited since the pre-Roman age. The Gulf is characterized by the contrast between highly polluted areas (Bagnoli-Coroglio, Eastern-Naples) and pristine sites identified as Marine Protected Areas (Punta Campanella, Regno di Nettuno). The macrosite includes two sampling stations, one for the study of plankton and one for the study of benthos. The plankton sampling area is located off the city of Naples, at the border between the eutrophic littoral area and the oligotrophic open waters. The benthic sampling site is occupied by the highly valuable Posidonia oceanica (L.) Delile meadows which extend over a wide bathymetric range along the Ischia Island coasts. A further peculiarity of this island stemming from its volcanic nature is represented by the CO2 emissions from the seabed which allow to study the adaptations of organisms and benthic ecosystems to acidification. In support to the observational activities, two MEDA-elastic buoys were installed in 2016 at a short distance from the coast, one off the Stazione Zoologica Anton Dohrn and the other off Bagnoli. The buoys are equipped with meteorological sensors, multi-parametric profiling probes and ADCP current-meters. High-frequency data are transmitted in real time via a broadband Wi-Fi bridge and also via the GSM network.

The Gulf of Naples (Central Tyrrhenian Sea, Western Mediterranean Sea) extends between 40��50'-40��32'N and 13��52'-14��28'E, with an area of 870 km2 and an average depth of 170 m. About 4 million people live along the coasts, which have been inhabited since the pre-Roman age. The Gulf is characterized by the contrast between highly polluted areas (Bagnoli-Coroglio, Eastern-Naples) and pristine sites identified as Marine Protected Areas (Punta Campanella, Regno di Nettuno). The macrosite includes two sampling stations, one for the study of plankton and one for the study of benthos. The plankton sampling area is located off the city of Naples, at the border between the eutrophic littoral area and the oligotrophic open waters. The benthic sampling site is occupied by the highly valuable Posidonia oceanica (L.) Delile meadows which extend over a wide bathymetric range along the Ischia Island coasts. A further peculiarity of this island stemming from its volcanic nature is represented by the CO2 emissions from the seabed which allow to study the adaptations of organisms and benthic ecosystems to acidification. In support to the observational activities, two MEDA-elastic buoys were installed in 2016 at a short distance from the coast, one off the Stazione Zoologica Anton Dohrn and the other off Bagnoli. The buoys are equipped with meteorological sensors, multi-parametric profiling probes and ADCP current-meters. High-frequency data are transmitted in real time via a broadband Wi-Fi bridge and also via the GSM network.

In the Mediterranean, Cystoseira sensu lato (s.l.) (Phaeophyceae) forests have sharply declined and restoration measures are needed to compensate for the loss. Assisted regeneration through the outplanting of seedlings grown ex-situ has proven to be a sustainable option. Optimizing mesocosm culture can maximize survival of the most critical embryonic stages and reduce long-term maintenance costs. Host-microbiome interactions could also play a crucial role in seedling development and welfare. In this context, we aimed to advance a cultivation protocol that stimulates the growth and fitness of Ericaria amentacea (Phaeophyceae) seedlings and identify the associated microbial biofilm communities. Seedlings were cultured in 6 treatments [i.e., filtered seawater (SW, C, Control), von Stoch-enriched SW (VS), VS + algal extract (VSA), algal extract-enriched SW: A1< A2< A3]. After the field, A2 seedlings had the highest cover (1372 ± 53.66 mm2), which was 1.8 and 1.9 times greater than in VS and VSA, respectively. The addition of the algal extract and nutrients significantly affected the structure and composition of the microbial community that shifted over time in each culture medium. We identified a treatment-specific microbial fingerprint. After the mesocosm phase, A2 was characterized by 4 unique taxa: Postechiella, Winogradskyella, Roseovarius and Arenibacter (Bacteria). Given the success of A2 seedlings, we propose the probiotic consortia candidates characterized by the unique treatment-taxa in conjunction with the shared taxon Psychroserpens (Bacteria, present in A1, A2, VSA, VS) and the reminder community. Within the holobiont concept, the effect of algal extract or nutrients on the algae and/or biofilm could have important consequences for tuning the overall interaction networks. Our study has shown that macroalgal restoration could benefit from both the use of commercial algal extract and tailored nutrient enrichment in ex-situ cultures and the identification of probiotic consortia candidates that promote seedling growth.